Yes, that is what killed F# effectively - on top of not having any killer frameworks. Though to be fair even Scala is dead. Making a language popular is tough.
F# has been an unwanted child of Microsoft, it actually adopted the language from Microsoft Research. As a language, F# is _very_ good (although not as good as the original OCaml, whose features had to be cut to be able to run on CLR). It's just not first-class citizen, so not everything may work with F#. And F#'s own development and features are blocked on CLR -- instead of F# charting its own path, each feature first has to be available for C#/CLR and only then will F# developers implement it (higher-kinded types are just one example).
But it's still much more pleasant "syntactic sugar to write the CIL bytecode" than C# can ever be.
> even Scala is dead
I beg to differ! Thankfully, Scala is very much not dead. Scala 3 is around the corner, with many more features and, even more importantly, several simplifications. And the community is also much larger compared to F# (or any other ML language, like Haskell). Innovation also takes place in the realm of libraries, like ZIO for example.
And here I am happily using it for greenfield projects, interfacing with popular ecosystems and just generally getting things done!
Right now it really feels like F# is taking off. It is bundled with .NET Core, fully open-source, has a better REPL experience with Nuget integration, Ionide and Fable just had a new releases...
I have been programming in F# full time for the past 7 years and I hope that rumours of its death are greatly exaggerated. Perhaps this comes from a point of view that if something is not growing 10x each year is dead?
It's not a JavaScript framework that has an average lifespan of a couple of years. It's a fully featured, complete, very productive language that makes programmers life easier and more enjoyable.